In recent years, various kinds of devices that are simple and that can detect analytes (a substance to be detected) contained in sample solutions by developing the sample solutions therein were proposed. Further, in-vitro diagnostic reagents and various kinds of devices for poison detection or the like were sold. One of the examples is a device using immunochromatography. In immunochromatography, no heavy equipment/instrument is required to perform judgment and measurement, and the operation is simple. In immunochromatography, a measurement result can be obtained merely by dropping a sample solution that may contain an analyte onto a carrier, and by keeping the sample solution standing for approximately 5 to 10 minutes. Therefore, the immunochromatography is a simple and quick method, and judgment and measurement with high specificity is possible. Hence, the immunochromatography is widely used, for example, in clinical laboratory examinations at hospitals, laboratory tests for research, and the like.
Meanwhile, many of bioactive substances, such as natural products, toxins, hormones, and pesticides, and environmental pollutants act on living organisms, even if the amounts of the substances are extremely small and even undetectable by using a conventional general immunochromatography method. Therefore, an immunochromatography method that can detect such substances quickly, easily and at high sensitivity is needed. For that purpose, in addition to simply dropping a sample solution containing an analyte onto a carrier, the following method is used to detect the analyte, for example. After the sample solution containing the analyte is dropped onto the carrier to immobilize the analyte on the carrier, the sample solution is washed away by a washing solution (washing liquid). Further, the immobilized analyte is placed in contact with a reaction substrate solution, an amplification solution or the like to detect amplified signals output from the analyte.
For example, Japanese Unexamined Patent Publication No. 2002-202307 (Patent Document 1) discloses an immunochromatography that can analyze an analyte at high sensitivity. In the method, an amplification solution, such as metal colloid, is dropped onto a detection portion. Further, Japanese Patent No. 3309977 (Patent Document 2) discloses a method for detecting signals. In the method, after a sample solution containing an analyte is placed in contact with an enzyme labeled antibody, the sample solution is caused to flow to a stationary phase carrier to which an analyte capture reagent has bound. Accordingly, the analyte—enzyme labeled antibody binds onto the carrier. Further, an enzyme substrate solution is caused to flow to the stationary phase carrier to make the enzyme substrate react, and signals are detected.
In the immunochromatography disclosed in Patent Document 1 and Patent Document 2, signals can be amplified by enzymes or silver. Therefore, it is possible to analyze a very small amount of analyte.
However, in the immunochromatography disclosed in Patent Document 1 and Patent Document 2, components of enzyme substrate solutions, signal amplification solutions, such as metal colloid amplification solutions, or other solutions, such as washing solution, may not be sent to the stationary phase carrier evenly, because of a difference in molecular mutual action, such as hydrophilicity/hydrophobicity and electrostatic mutual actions, with the stationary phase carrier. Therefore, it is difficult to make the reaction progress evenly or uniformly in the stationary phase carrier. Hence, highly accurate and highly sensitive detection is limited.